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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,639 records · Page 91
All sourcesNASA NTRSDOE OSTI
DOE OSTI2010

Crystal Plasticity Finite Element Analysis of Loading-Unloading Behaviour in Magnesium Alloy Sheet

Magnesium alloy sheets exhibit strong inelastic response during unloading. In this study crystal plasticity finite element analysis of loading-unloading behaviour during uniaxial tension in a rolled magnesium alloy sheet was carried out, and the mechanism of this inelastic response was examined in detail in terms of macroscopic and mesoscopic deformations. The unloading behaviour obtained by the simulation was in good agreement with the experiment in terms of variation with stress of instantaneous tangent modulus during unloading. Variations of activities of each family of slip systems during the deformation showed that the activation of basal slip systems is the largest during unloading, and the slip direction during unloading is opposite from during loading. These results indicated that one of the factors of the inelastic behaviour during unloading is the fact that the basal slip systems are easily activated during unloading because of their low strengths.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Coordinated Optimal Control of Constrained DERs

In this paper, a coordinated optimal control is designed to simultaneously satisfy multiple power system objectives at the distribution network level. With high penetration of renewables, traditional generation and control may not be enough to compensate for intermittent changes in net load. Dynamic coordination of battery storage devices and demand response at aggregated distributed energy resource (DER) sites becomes necessary to maintain power system operation, however, each dynamic power component operates at different time scales. Frequency stabilization can be achieved by designing optimal controls for traditional generation, storage devices and demand response. The proposed optimal controls naturally render frequency separation of these load balancing mechanisms. Given a 24-hour net load forecast, optimal tracking control inputs are designed subject to constraints of selected system elements to ensure optimal performance of the power system. Simulation results are presented and discussed.

Harvey, Roland↗
NASA NTRS1989

The effect of mass loading on the temperature of a flowing plasma

How the addition of ions at rest (mass loading) affects the temperature of a flowing plasma in a MHD approximation is investigated, using analytic theory and time dependent, three-dimensional MHD simulations of plasma flow past Io. The MHD equations show that the temperature can increase or decrease relative to the background, depending on the local sonic Mach number M(S), of the flow. For flows with M(S) of greater than sq rt 9/5 (when gamma = 5/3), mass loading increases the plasma temperature. However, the simulations show a nonlinear response to the addition of mass. If the mass loading rate is large enough, the temperature increase may be smaller than expected, or the temperature may actually decrease, because a large mass loading rate slows the flow and decreases the thermal energy of the newly created plasma.

Linker, Jon A.↗
DOE OSTI2022

Schema Grapher

PNNL contributions to project site managed by federal agency. Schema Grapher is an application that takes in CSV datasets and converts them to RDF for loading into a graph database. Schema Grapher is responsible for the extract and transform part of an ETL (i.e., extract, transform, load) pipeline.

Avila, Andrew↗
NASA NTRS1994

TOGA/COARE AMMR 1992 data processing

The complete set of Tropical Ocean and Global Atmosphere (TOGA)/Coupled Ocean Atmosphere Response Experiment (COARE) flight data for the 91.65 GHz Airborne Meteorological Radiometer (AMMR92) contains data from nineteen flights: two test flights, four transit flights, and thirteen experimental flights. The data flight occurred between December 16, 1992 and February 28, 1993. Data collection from the AMMR92 during the first ten flights of TOGA/COARE was performed using the executable code TSK30041. These are IBM PC/XT programs used by the NASA Goddard Space Flight Center (GSFC). During one flight, inconsistencies were found during the operation of the AMMR92 using the GSFC data acquisition system. Consequently, the Georgia Tech (GT) data acquisition system was used during all successive TOGA/COARE flights. These inconsistencies were found during the data processing to affect the recorded data as well. Errors are caused by an insufficient pre- and post-calibration setting period for the splash-plate mechanism. The splash-plate operates asynchronusly with the data acquisition system (there is no position feedback to the GSFC or GT data system). This condition caused both the calibration and the post-calibration scene measurement to be corrupted on a randomly occurring basis when the GSFC system was used. This problem did not occur with the GT data acquisition system due to sufficient allowance for splash-plate settling. After TOGA/COARE it was determined that calibration of the instrument was a function of the scene brightness temperature. Therefore, the orientation error in the main antenna beam of the AMMR92 is hypothesized to be caused by misalignment of the internal 'splash-plate' responsible for directing the antenna beam toward the scene or toward the calibration loads. Misalignment of the splash-plate is responsible for 'scene feedthrough' during calibration. Laboratory investigation at Georgia Tech found that each polarization is affected differently by the splash-plate alignment error. This is likely to cause significant and unique errors in the absolute calibration of each channel.

Kunkee, D. B.↗
NASA NTRS1997

Effects of static fingertip loading on carpal tunnel pressure

The purpose of this study was to explore the relationship between carpal tunnel pressure and fingertip force during a simple pressing task. Carpal tunnel pressure was measured in 15 healthy volunteers by means of a saline-filled catheter inserted percutaneously into the carpal tunnel of the nondominant hand. The subjects pressed on a load cell with the tip of the index finger and with 0, 6, 9, and 12 N of force. The task was repeated in 10 wrist postures: neutral; 10 and 20 degrees of ulnar deviation; 10 degrees of radial deviation; and 15, 30, and 45 degrees of both flexion and extension. Fingertip loading significantly increased carpal tunnel pressure for all wrist angles (p = 0.0001). Post hoc analyses identified significant increase (p < 0.05) in carpal tunnel pressure between unloaded (0 N) and all loaded conditions, as well as between the 6 and 12 N load conditions. This study demonstrates that the process whereby fingertip loading elevates carpal tunnel pressure is independent of wrist posture and that relatively small fingertip loads have a large effect on carpal tunnel pressure. It also reveals the response characteristics of carpal tunnel pressure to fingertip loading, which is one step in understanding the relationship between sustained grip and pinch activities and the aggravation or development of median neuropathy at the wrist.

NASA Center ARC↗
NASA NTRS1975

NECAP: NASA's Energy-Cost Analysis Program. Part 1: User's manual

The NECAP is a sophisticated building design and energy analysis tool which has embodied within it all of the latest ASHRAE state-of-the-art techniques for performing thermal load calculation and energy usage predictions. It is a set of six individual computer programs which include: response factor program, data verification program, thermal load analysis program, variable temperature program, system and equipment simulation program, and owning and operating cost program. Each segment of NECAP is described, and instructions are set forth for preparing the required input data and for interpreting the resulting reports.

Henninger, R. H.↗
NASA NTRS1976

A seat cushion to provide realistic acceleration cues for aircraft simulators

A seat cushion to provide acceleration cues for aircraft simulator pilots was built, performance tested, and evaluated. The four cell seat, using a thin air cushion with highly responsive pressure control, attempts to reproduce the same events which occur in an aircraft seat under acceleration loading. The pressure controller provides seat cushion responses which are considered adequate for current high performance aircraft simulations. The initial tests of the seat cushions have resulted in excellent pilot opinion of the cushion's ability to provide realistic and useful cues to the simulator pilot.

Ashworth, B. R.↗
NASA NTRS1991

Thermo-mechanical response predictions for metal matrix composite laminates

An analytical micromechanical model is employed for prediction of the stress-strain response of metal matrix composite laminates subjected to thermomechanical loading. The predicted behavior of laminates is based upon knowledge of the thermomechanical response of the transversely isotropic, elastic fibers and the elastic-viscoplastic, work-hardening matrix. The method is applied to study the behavior of silicon carbide/titanium metal matrix composite laminates. The response of laminates is compared with that of unidirectional lamina. The results demonstrate the effect of cooling from a stress-free temperature and the mismatch of thermal and mechanical properties of the constituent phases on the laminate's subsequent mechanical response. Typical results are presented for a variety of laminates subjected to monotonic tension, monotonic shear and cyclic tensile/compressive loadings.

Aboudi, J.↗
DOE OSTI2024

Nonlinear behavior in high-frequency aggregate control of thermostatically controlled loads

Coordinated control of electric loads can provide valuable grid services, such as frequency regulation. However, due to the nonlinear characteristics of such load ensembles, it is important to systematically analyze their behavior and establish a thorough understanding of undesirable phenomena that can potentially arise. In this paper, we analyze the frequency response of an aggregate control scheme, with the goal of exploring controller performance limits. We show that rapid switching commands can induce oscillations in the power output due to the inherent lockout mechanism of the underlying devices. Here, we demonstrate that highly detailed aggregate models are required to capture such phenomena. Such models enable deeper understanding of the control boundaries and therefore play an important role in avoiding the introduction of undesirable effects on the grid.

24 POWER TRANSMISSION AND DISTRIBUTION↗
NASA NTRS1992

Design, analysis, and testing of a metal matrix composite web/flange intersection

An experimental and analytical program to study the local design details of a typical T-shaped web/flange intersection made from a metal matrix composite is described. Loads creating flange bending were applied to specimens having different designs and boundary conditions. Finite element analyses were conducted on models of the test specimens to predict the structural response. The analyses correctly predict failure load, mode, and location in the fillet material in the intersection region of the web and the flange when specimen quality is good. The test program shows the importance of fabrication quality in the intersection region. The full-scale test program that led to the investigation of this local detail is also described.

Biggers, S. B.↗
NASA NTRS1971

A method for determining the response of space shuttle to atmospheric turbulence. Volume 1: Space shuttle turbulence response

A computer program has been developed and demonstrated that can analyze the response of space shuttle to atmospheric turbulence. The method developed accounts for propellant slosh, gimballed engine, and stability augmentation system (SAS) coupling with the elastic vehicle. Statistical outputs are generated that relate vehicle loads and accelerations to level of random turbulence. For discrete turbulence descriptions, response time-histories are computed. Preliminary turbulence response analyses of space shuttle were conducted for one ascent and one booster flyback subsonic flight condition. The ascent case considered both symmetric and antisymmetric boundary conditions, while only the symmetric analysis was conducted for booster flyback. The three conditions were analyzed with SAS active and inactive, but apparent instabilities with SAS active (arising from improper gains) invalidated the results. Load and acceleration responses in all cases, however, were well within vehicle design limits.

Source record↗
DOE OSTI2019

Transactive Control Design for Commercial Buildings to Provide Demand Response

Transactive coordination and control is a new type of distributed strategy that is designed to engage various self-interested distributed energy resources such as controllable loads, distributed generators, and energy storage for providing demand response. In this paper, a novel transactive control design is proposed for commercial buildings to coordinate the electricity demand of the package rooftop air conditioning units (RTUs) for demand response. Such a coordination is realized by introducing a local relationship between the temperature setpoint and the market clearing price. With the proposed market-based control, the demand of individual RTUs is adjusted by changing their temperature setpoints as a response to the market clearing prices. Two dierent scenarios of demand response are considered herein. One is to limit the peak demand of commercial buildings, in which a new market clearing strategy based on proportionalintegral- derivative control with respect to the demand limit is proposed. The other one is to perform price responsive control, in which the total demand of commercial buildings will respond to the real-time pricing. The proposed transactive strategy is also tested and demonstrated on a real occupied building located at Pacic Northwest National Laboratory. The eld testing results conrm the eectiveness of the proposed transactive coordination and control for commercial building with RTUs to provide demand response.

Huang, Sen↗
NASA NTRS1988

Computational aspects of sensitivity calculations in transient structural analysis

A key step in the application of formal automated design techniques to structures under transient loading is the calculation of sensitivities of response quantities to the design parameters. This paper considers structures with general forms of damping acted on by general transient loading and addresses issues of computational errors and computational efficiency. The equations of motion are reduced using the traditional basis of vibration modes and then integrated using a highly accurate, explicit integration technique. A critical point constraint formulation is used to place constraints on the magnitude of each response quantity as a function of time. Three different techniques for calculating sensitivities of the critical point constraints are presented. The first two are based on the straightforward application of the forward and central difference operators, respectively. The third is based on explicit differentiation of the equations of motion. Condition errors, finite difference truncation errors, and modal convergence errors for the three techniques are compared by applying them to a simple five-span-beam problem. Sensitivity results are presented for two different transient loading conditions and for both damped and undamped cases.

Greene, William H.↗
NASA NTRS1989

Computational aspects of sensitivity calculations in transient structural analysis

A key step in the application of formal automated design techniques to structures under transient loading is the calculation of sensitivities of response quantities to the design parameters. This paper considers response quantities to the design parameters. This paper considers structures with general forms of damping acted on by general transient loading and addresses issues of computational errors and computational efficiency. The equations of motion are reduced using the traditional basis of vibration modes and then integrated using a highly accurate, explicit integration technique. A critical point constraint formulation is used to place constraints on the magnitude of each response quantity as a function of time. Three different techniques for calculating sensitivities of the critical point constraints are presented. The first two are based on the straightforward application of the forward and central difference operators, respectively. The third is based on explicit differentiation of the equations of motion. Condition errors, finite difference truncation errors, and modal convergence errors for the three techniques are compared by applying them to a simple five-span-beam problem. Sensitivity results are presented for two different transient loading conditions and for both damped and undamped cases.

Greene, William H.↗
NASA NTRS1986

Prediction of blade stresses due to gust loading

An analysis is developed for investigating the response of a rotor-fuselage system in a three-dimensional gust field wherein the gust velocity conponents can have arbitrary variation in space and time. Each rotor blade undergoes flap bending, lag bending and torsional deflections. The blades are divided into beam elements and each element consists of fifteen nodal degrees of freedom. Quasi-steady strip theory is used to obtain the aerodynamic loads. Unsteady aerodynamic effects are introduced through dynamic inflow modeling. Dynamic stall and reverse flow effects are also included. The fuselage is allowed five degrees of freedom: vertical, longitudinal, lateral, pitch and roll motions. The gust response equations are linearized about the vehicle trim state and the blade steady-state deflected position, and then solved by time integration. The blade bending moments, which determine blade stresses, are evaluated using the force summation technique. Systematic studies are made to identify the importance of several parameters including dynamic stall, forward speed, lag stiffness, gust profile, gust penetration rate and gust velocity direction.

Bir, Gunjit↗
DOE OSTI2026

Electrochemically recovered struvite matches conventional fertilizers in soil nutrient supply

Phosphorus (P) is an essential macronutrient for agriculture, yet global reliance on finite phosphorite reserves raises concerns about long-term food and nutrient security. Struvite (MgNH 4 PO 4 ·6H 2 O), a mineral recovered from municipal wastewater, represents a sustainable and circular source of P, but uncertainty remains regarding its nutrient availability relative to conventional fertilizers. This study evaluated the fertilizer value and environmental safety of electrochemically recovered struvite (RecoP) in comparison with diammonium phosphate (DAP), triple superphosphate (TSP), and rock phosphate (RockP). Nutrient availability, potential contaminant concentrations, and soil P and nitrogen (N) dynamics were assessed using standardized chemical analyses and an 8-week incubation experiment across three soils with contrasting soil types. RecoP contained 14.7% citrate-soluble P, significantly greater than RockP and comparable to DAP and TSP. Across all soils, RecoP increased both readily available and moderately labile P pools (p < 0.01), matching the performance of conventional fast-release fertilizers. Despite containing approximately half the total of DAP, RecoP stimulated nitrification rates that were 2.2 times greater than the control and exceeded those of TSP, suggesting that fertilizer-derived N bioavailability, rather than total N loading, governed microbial N transformation responses. Concentrations of potentially toxic elements in RecoP were consistently well below US Environmental Protection Agency regulatory limits thresholds. Collectively, these results indicate that RecoP functions as a readily available source of both P and N, comparable to widely used conventional fertilizers, while meeting environmental safety standards. RecoP therefore represents a viable component of sustainable nutrient management strategies that support P recycling and agricultural productivity.

Kharal, Sudarshan [Ohio Univ., Athens, OH (United ↗
DOE OSTI2022

Computational Design of a Simple Flyer Plate Launcher

The response of materials to shock loading is important to understand for a variety of applications. When shock physics emerged during and after WWII, direct explosive loading or explosively driven plate impact was the primary tool for these studies. Subsequent decades have seen the widespread use of large caliber guns for plate impact studies, laser-shock facilities and pulsed power facilities. INL currently lacks a gun suitable for plate impact or explosives casting and machining facilities; however, it does possess explosives use and handling capabilities. An option for performing plate impact experiments was needed, therefore continuum scale models were utilized to explore a few simple donor-acceptor explosive plane wave lens designs, one of which could be hand packed with plastic explosives to launch flyer plates. 2D simulations were performed to study different geometries in an effort to minimize the difference in shock arrival across the central portion of a small copper flyer plate. A shock wave arrival time difference under 50 ns across 50 percent of the center of the flyer was achieved with a few designs. This work summarizes the computational models and results.

36 MATERIALS SCIENCE↗